Surrogate models are used to dramatically improve the design efficiency of numerical aerodynamic shape optimization, where high-fidelity, expensive computational fluid dynamics (CFD) is often ...employed. Traditionally, in adaptation, only one single sample point is chosen to update the surrogate model during each updating cycle, after the initial surrogate model is built. To enable the selection of multiple new samples at each updating cycle, a few parallel infilling strategies have been developed in recent years, in order to reduce the optimization wall clock time. In this article, an alternative parallel infilling strategy for surrogate-based constrained optimization is presented and demonstrated by the aerodynamic shape optimization of transonic wings. Different from existing methods in which multiple sample points are chosen by a single infill criterion, this article uses a combination of multiple infill criteria, with each criterion choosing a different sample point. Constrained drag minimizations of the ONERA-M6 and DLR-F4 wings are exercised to demonstrate the proposed method, including low-dimensional (6 design variables) and higher-dimensional problems (up to 48 design variables). The results show that, for surrogate-based optimization of transonic wings, the proposed method is more effective than the existing parallel infilling strategies, when the number of initial sample points are in the range from
N
v
to
8N
v
(
N
v
here denotes the number of design variables). Each case is repeated 50 times to eliminate the effect of randomness in our results.
Abstract
We present a timing study of the short-period eclipsing cataclysmic variable (CV) HT Cas. Based on new eclipse times derived from our photometric monitoring and archival optical data, ...combined with historical timings, spanning ∼42 yr, we detect a secular decrease in the orbital period at a rate of
P
̇
=
−
1.32
×
10
−
12
ss
−
1
and a cyclic period wiggle with an amplitude of 79.3 s and a period of 30.28 yr. We find that neither gravitational radiation nor magnetic braking can explain the observed decrease rate, suggesting the presence of additional angular momentum loss (AML). The empirical consequential AML (eCAML) model developed by Schreiber et al. can well match the observed orbital decay in HT Cas, and the physical mechanism for eCAML is most likely attributable to the frictional AML following nova eruptions. As for the cyclic variation, the best explanation is the influence of an unseen companion in orbit around the binary. The derived orbital parameters reveal that the hypothetical third body could be a giant planet with mass of
M
3
≃ 14
M
Jup
that is moving on a highly eccentric orbit (
e
= 0.82). Taken together the results of the present study suggest that HT Cas is a unique triple system containing a high-eccentricity giant planet and it has the potential to become an ideal laboratory in which to test models of CV evolution.
The accurate estimation of the tire–road friction coefficient plays a significant role in the vehicle dynamics control. The estimation method should be timely and reliable for the controlling ...requirements, which means the contact friction characteristics between the tire and the road should be recognized before the interference to ensure the safety of the driver and passengers from drifting and losing control. In addition, the estimation method should be stable and feasible for complex maneuvering operations to guarantee the control performance as well. A signal fusion method combining the available signals to estimate the road friction is suggested in this paper on the basis of the estimated ones of braking, driving and steering conditions individually. Through the input characteristics and the states of the vehicle and tires from sensors the maneuvering condition may be recognized, by which the certainty factors of the friction of the three conditions mentioned above may be obtained correspondingly, and then the comprehensive road friction may be calculated. Experimental vehicle tests validate the effectiveness of the proposed method through complex maneuvering operations; the estimated road friction coefficient based on the signal fusion method is relatively timely and accurate to satisfy the control demands.
•Simple method to estimate road friction for ABS, TCS and AYC for ground test.•No extra pressure sensors and other apparatus.•Combine the road friction for ABS, TCS and AYC to improve robustness and accuracy.•Tested under complex maneuvering operations.•Consider the driving and steering combined condition.
A gradient nanostructured (GNS) surface layer was generated in a dual-phase Cu-Ag alloy by means of surface mechanical grinding treatment at liquid nitrogen temperature. With a decreasing depth in ...the surface layer, the coarse-grained microstructure of Cu matrix and Ag precipitates gradually converts into a nanolaminated structure of Ag- and Cu-rich phases with simultaneous chemical mixing, and finally forms a homogeneous single-phase supersaturated solid solution (SSS) nanostructure. Accordingly, a dislocation-mediated transportation mechanism was proposed to dominate the chemical mixing of Ag and Cu atoms, i.e., dislocations interacting with solution atoms penetrate the Cu/Ag interface and glide in the neighboring solvent-phase lamella.
•A gradient nanostructured (GNS) surface layer was generated in a dual-phase Cu-Ag alloy.•Intermixing of Cu- and Ag-rich phases simultaneously occurs in the GNS surface layer.•A dislocation-mediated transportation mechanism was proposed to dominate the chemical mixing of Ag and Cu atoms.
Dysregulated microRNAs (miRNAs) have an important role in many malignant tumors. However, elucidating the roles of miRNAs in cancer biology, especially in epithelial cancers, remains an ongoing ...process. In this study, we show that both miR-143 and miR-145, which belong to the same miRNA cluster, can negatively modulate expression of their target gene, MDM2. The miR-143 and miR-145 is posttranscriptionally activated by upregulated p53, thereby generating a short miRNAs-MDM2-p53 feedback loop. Re-expression of these miRNAs suppresses cellular growth and triggers the apoptosis of epithelial cancer, in vitro and in vivo, by enhancing p53 activity via MDM2 turnover. Moreover, the miRNA-dependent MDM2 turnover contributes to the equilibrium of repeated p53 pulses in response to DNA damage stress. These findings suggest that MDM2 dysregulation caused by downregulation of miR-143 and miR-145 contributes to epithelial cancer development and has a key role in regulating cellular proliferation and apoptosis. Re-expression of miR-143 and miR-145 may be a reasonable strategy for treatment of epithelial cancers.
The WD+MS channel of the single-degenerate scenario is currently favorable for progenitors of Type Ia supernovae (SNe Ia). Incorporating the results of detailed binary evolution calculations for this ...channel into the latest version of a binary population synthesis code, I obtained the distributions of many properties of the companion stars at the moment of SN explosion. The properties can be verified by future observations.
About 3196 EA-type binaries (EAs) were observed by LAMOST by 2017 June 16 and their spectral types were derived. Meanwhile, the stellar atmospheric parameters of 2020 EAs were determined. In this ...paper, those EAs are cataloged and their physical properties and evolutionary states are investigated. The period distribution of EAs suggests that the period limit of tidal locking for the close binaries is about 6 days. It is found that the metallicity of EAs is higher than that of EW-type binaries (EWs), indicating that EAs are generally younger than EWs and they are the progenitors of EWs. The metallicities of long-period EWs ( days) are the same as those of EAs with the same periods, while their values of Log (g) are usually smaller than those of EAs. These support the evolutionary process that EAs evolve into long-period EWs through the combination of angular momentum loss (AML) via magnetic braking and case A mass transfer. For short-period EWs, their metallicities are lower than those of EAs, while their gravitational accelerations are higher. These reveal that they may be formed from cool short-period EAs through AML via magnetic braking with little mass transfer. For some EWs with high metallicities, they may be contaminated by material from the evolution of unseen neutron stars and black holes or they have third bodies that may help them to form rapidly through a short timescale of pre-contact evolution. The present investigation suggests that the modern EW populations may have formed through a combination of these mechanisms.
This work focuses on the size distribution of sneeze droplets exhaled immediately at mouth. Twenty healthy subjects participated in the experiment and 44 sneezes were measured by using a laser ...particle size analyser. Two types of distributions are observed: unimodal and bimodal. For each sneeze, the droplets exhaled at different time in the sneeze duration have the same distribution characteristics with good time stability. The volume-based size distributions of sneeze droplets can be represented by a lognormal distribution function, and the relationship between the distribution parameters and the physiological characteristics of the subjects are studied by using linear regression analysis. The geometric mean of the droplet size of all the subjects is 360.1 µm for unimodal distribution and 74.4 µm for bimodal distribution with geometric standard deviations of 1.5 and 1.7, respectively. For the two peaks of the bimodal distribution, the geometric mean (the geometric standard deviation) is 386.2 µm (1.8) for peak 1 and 72.0 µm (1.5) for peak 2. The influences of the measurement method, the limitations of the instrument, the evaporation effects of the droplets, the differences of biological dynamic mechanism and characteristics between sneeze and other respiratory activities are also discussed.
Context. The binary fraction among extreme horizontal branch (EHB) stars in Galactic globular clusters (GCs) is an order of magnitude lower than the binary fraction among their counterparts, field ...hot subdwarfs. This casts serious doubt on their formation channels. Aims. In this Letter, I explain the difference between the field and the cluster EHB stars with the binary model of Han et al. (2002, MNRAS, 336, 449; 2003, MNRAS, 341, 669) for the formation of EHB stars. Methods. With the binary population synthesis code of Han et al. (2002, 2003), I follow the evolution of simple stellar populations resulting from single star bursts (note that Han et al. 2002, 2003, adopted a constant star formation rate over the last 15 Gyr for the production of field EHB stars), and obtain EHB stars at different stellar population ages. Results. I found that the binary fraction among EHB stars decreases with the stellar population age. The fraction of EHB binaries with orbital periods P < 5 d is ~2.5% for a stellar population of 10 Gyr from the standard simulation set. Conclusions. The binary model of Han et al. (2002, 2003) is able to explain the lack of EHB binaries in globular clusters. I also propose that the precise determination of the physical parameters of close EHB binaries in GCs can lead to the strictest constraint on common-envelope ejection efficiency.
PDF
